Chromene compound

ABSTRACT

A chromene compound represented by the general formula (1), 
                 
         wherein R 1  to R 4  are hydrogen atoms, hydroxyl groups, alkyl groups, alkoxy groups, substituted amino groups or halogen atoms, R 1  to R 4  may be bonded together to form a ring, R 5  and R 6  are alkyl groups, aryl groups or heteroaryl groups, or R 5  and R 6  together may form a ring, a cyclic group containing X or Y is an aromatic hydrocarbon group or an aromatic heterocyclic group, and a divalent group Z is an alkylene group.       

     This compound exhibits excellent photochromic properties, such as small initial color, a large fading rate, excellent resistance and developing a color tone of a neutral tint.

This application is a 371 of PCT/JP02/11935 filed Nov. 15, 2002.

TECHNICAL FIELD

The present invention relates to a novel chromene compound and to the use of the chromene compound.

BACKGROUND ART

Photochromism is a phenomenon that is drawing attention in recent several years and is a reversible action of a compound which quickly changes its color (called color development) when it is irradiated with light containing ultraviolet rays such as sunlight or light of a mercury lamp and resumes its initial color (called color fading) when it is no longer irradiated with light but is placed in a dark place. The compound having this property is called photochromic compound. One of the applications of the photochromic compound may be a dimmer material for lenses of sunglasses.

When used for the above application, the photochromic compound must satisfy the following photochromic properties:

-   {circle around (1)} Color changes stably when the color development     and color fading are repeated (favorably resistance the repetition). -   {circle around (2)} Has a small coloring degree in a state of not     irradiated with light (has a small initial color). -   {circle around (3)} Exhibits a quick fading rate when the     irradiation with light is discontinued.

In recent years, further, it has been desired to realize a compound which is capable of developing a neutral tint such as grey, brown or green. The compound that develops such a neutral tint must have two absorption bands (420 to 520 nm and 520 to 620 nm) of nearly the same absorption intensities in the wavelength region of visible rays.

In order to satisfy the above requirements, there have heretofore been synthesized a variety of photochromic compounds without, however, any common nature in their structures.

U.S. Pat. No. 5,783,116 discloses a chromene compound represented by the following formula (A),

This chromene compound, however, has only one absorption band. Therefore, this chromene compound is not capable of developing a color tone of a neutral tint and, besides, exhibits a slow fading rate.

Further, PCT Patent Application WO00/15628 discloses a chromene compound represented by the following formula (B),

To satisfy the requirement of coloring spectrum of the above-mentioned neutral tint, this chromene compound develops a neutral tint of brown color while developing a small initial color involving, however, a problem of a slow fading rate.

The present inventors have previously discovered a chromene compound represented by the following general formula (C) among the compounds disclosed in their patent application (Japanese Unexamined Patent Publication (Kokai) 11-154272).

This chromene compound exhibits a largefading rate. Due to a large difference in the absorption intensity between the two absorption bands, however, this chromene compound is capable of developing a single blue color only.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to further improve photochromic properties of the conventional compounds while solving their problems. Namely, the present invention provides a chromene compound that exhibits a small initial color, a large fading rate, a good resistance and that develops a color tone of a neutral tint.

Namely, the present invention provides a chromene compound represented by the following formula (1),

-   -   wherein R¹, R², R³ and R⁴ are, independently from each other,         hydrogen atoms, hydroxyl groups, alkyl groups, alkoxy groups,         aralkyl groups, aralkoxy groups, amino groups, substituted amino         groups, cyano groups, nitro groups, halogen atoms, halogenoalkyl         groups or halogenoalkoxy groups,     -   R¹ and R² together, and R³ and R⁴ together, may form rings, and     -   either R¹ or R² and either R³ or R⁴ together may form a ring,     -   R⁵ and R⁶ are, independently from each other, alkyl groups,         substituted or unsubstituted aryl groups, or substituted or         unsubstituted heteroaryl groups, or     -   R5 and R6 together may form a ring, a trivalent cyclic group         represented by the following formula (2),     -   and a trivalent cyclic group represented by the following         formula (3),     -   are, independently from each other, substituted or         unsubsttituted aromatic hydrocarbon groups or substituted or         unsubstituted aromatic heterocyclic groups, and     -   a divalent group Z is the one presented by the following         formula (4) or (5),     -   wherein R⁷, R⁸ and R⁹ are, independently from each other,         alkylene groups, B and B′ are, independently from each other,         imino groups, substituted imino groups, oxy groups, thio groups,         carbonyl groups, cycloalkylene groups, cycloalkylidene groups,         or substituted or unsubstituted arylene groups, and m, n, p and         q are 0 or 1.

According to the present invention, further, there are provided a photochromic material comprising a chromene compound represented by the above general formula (1), and a photochromic optical material containing the chromene compound.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a diagram of a proton nuclear magnetic resonance spectrum of a compound of Example 1.

BEST MODE FOR CARRYING OUT THE INVENTION

Described below are the groups in the above-mentioned general formula (1).

Trivalent Cyclic Groups [Formulas (2) and (3)]

The trivalent cyclic groups represented by the following formulas (2) and (3),

in the above-mentioned general formula (1) are, independently from each other, substituted or unsubstituted aromatic hydrocarbon groups, or substituted or unsubstituted aromatic heterocyclic groups.

Though there is no particular limitation, the aromatic hydrocarbon groups are preferably those having 6 to 18 carbon atoms (without including carbon atoms of the substituent). As the preferred aromatic hydrocarbon groups, there can be exemplified trivalent groups derived from a benzene ring, such as benzene, naphthalene and phenanthrene, and trivalent groups derived from a condensed ring formed by the condensation of 2 to 4 benzene rings. A trivalent group derived from a benzene ring is particularly desired.

Though there is no particular limitation, it is desired that the aromatic heterocyclic group is a trivalent group comprising an aromatic heterocyclic ring selected from a 5-membered ring or a 6-membered ring containing oxygen atom, sulfur atom or nitrogen atom; a condensed heterocyclic ring in which the above 5-membered or 6-membered heterocyclic ring is condensed with a benzene ring; or a condensed heterocyclic ring in which the aromatic hydrocarbon ring such as benzene ring is condensed with the above heterocyclic ring of the 5-membered ring or the 6-membered ring. As a preferred aromatic heterocyclic ring, there can be exemplified trivalent groups derived from a nitrogen-containing heterocyclic ring, such as pyridine, quinoline, dihydroquinoline, pyrrole and indole; trivalent groups derived from an oxygen-containing heterocyclic ring, such as furane and benzofurane; and trivalent groups derived from a sulfur-containing heterocyclic ring, such as thiophene and benzothiophene.

The above-mentioned aromatic hydrocarbon groups and the aromatic heterocyclic groups may have a substituent (hereinafter written as Rsb).

As the substituent (Rsb), there can be exemplified hydroxyl group; alkyl group; cycloalkyl group; alkoxy group; aralkyl group; aralkoxy group; amino group; substituted amino group; cyano group; nitro group; substituted or unsubstituted aryl group; substituted or unsubstituted heteroaryl group; halogen atom; halogenoalkyl group; halogenoalkoxy group; and substituted or unsubstituted heterocyclic group having a nitrogen atom as a hetero atom, and is bonded to the aromatic hydrocarbon group or to the aromatic heterocyclic group via the nitrogen atom (this heterocyclic group may further form a condensed heterocyclic group being condensed with an aromatic hydrocarbon ring or an aromatic heterocyclic ring).

Further, the substituent (Rsb) may be a group represented by the following formula (6) or (7), —W[(C₂H₄O)_(x)(C₃H₆O)_(y)(C₄H₈O)_(z)]_(a)—V  Formula (6):

-   -   wherein W is —C(═O)O—, —CH₂O—, —OC(═O)—, —N(R^(a))C(═O)—,         —N[C(═O)—]₂, —N(R^(a))—, —N(R^(a))CON(H)—, >N—, an oxygen atom         or a sulfur atom, x, y and z are integers of 0 to 50, the total         number of x, y and z is 1 to 50, a is 1 when W is —C(═O)O—,         —CH₂O—, —OC(═O)—, —N(R^(a))C(═O)—, —N(R^(a))—, —N(R^(a))CON(H)—,         an oxygen atom or a sulfur atom, and is 2 when W is —N[C(═O)—]₂         or >N—, V is a hydrogen atom, a (meth)acryloyl group, a group         having an epoxy group with 1 to 5 carbon atoms, a group having a         carboxyl group with 1 to 5 carbon atoms, an oxorane group, an         aminoalkyl group with 1 to 6 carbon atoms or an oxylanylmethyl         group, and R^(a) is a hydrogen atom or an alkyl group having 1         to 20 carbon atoms,         —W[(C₂H₄O)_(x′)(C₃H₆O)_(y′)(C₄H₈O)_(z′)]_(b)—T[(C₂H₄O)_(x″)(C₃H₆O)_(y″)(C₄H₈O)_(z″)]_(c)—V  Formula         (7):     -   wherein, T is a divalent organic residue having 5 to 20 carbon         atoms and containing a cyclic group, W and V are as defined in         the formula (6), x′, y′, z′, x″, y″ and z″ are the same as x, y         and z in the formula (6).

The above-mentioned substituent (Rsb) will now be described.

Though there is no particular limitation, the alkyl group is usually the one having 1 to 4 carbon atoms. Preferred examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, and tert-butyl group.

Though there is no particular limitation, the cycloalkyl group is usually an alkyl group having 3 to 12 carbon atoms. Preferred examples of the alkyl group include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group and cyclooctyl group.

Though there is no particular limitation, the alkoxy group is usually the one having 1 to 5 carbon atoms. Concrete examples of the preferred alkoxy group include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group and tert-butoxy group.

Though there is no particular limitation, the aralkyl group is usually the one having 7 to 11 carbon atoms. Preferred examples of the aralkyl group include benzyl group, phenylethyl group, phenylpropyl group and phenylbutyl group.

Though there is no particular limitation, it is desired that the aralkoxy group is the one having 6 to 10 carbon atoms. Preferred examples of the aralkoxy group include phenoxy group and naphthoxy group.

Though there is no particular limitation, the substituted amino group is an amino group having an alkyl group or an aryl group as the substituted group, such as an alkylamino group, a dialkylamino group, an arylamino group or a diarylamino group. Concrete examples of the preferred substituted amino group include methylamino group, ethylamino group, phenylamino group, dimethylamino group, diethylamino group and diphenylamino group.

Though there is no particular limitation, the unsubstituted aryl group is preferably the one having 6 to 10 carbon atoms, such as phenyl group and naphthyl group.

Though there is no particular limitation, the unsubstituted heteroaryl group is preferably the one containing oxygen atom, sulfur atom or nitrogen atom as a hetero atom, and having 4 to 12 atoms for forming a ring. Preferred examples of the unsubstituted heteroaryl group include thienyl group, furyl group, pyrrolinyl group, pyridyl group, benzothienyl group, benzofuranyl group and benzopyrrolinyl group.

As the substituent (group substituted for 1 or 2 or more hydrogen atoms of the unsubstituted aryl group or of the unsubstituted heteroaryl group) possessed by the substituted aryl group and the substituted heteroaryl group, there can be exemplified those which are the same as those exemplified for the substituent (Rsb).

As the halogen atom, there can be exemplified a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

As the halogenoalkyl group, there can be exemplified the above-mentioned alkyl groups of which 1 or 2 or more hydrogen atoms are substituted by fluorine atoms, chlorine atoms or bromine atoms. Preferred examples of the halogenoalkyl group include fluoromethyl group, difluoromethyl group and trifluoromethyl group.

As the halogenoalkoxy group, there can be exemplified the above-mentioned alkoxy groups of which 1 or 2 or more hydrogen atoms are substituted with fluorine atoms, chlorine atoms or bromine atoms. Particularly preferred examples of the halogenoalkoxy group include fluoromethoxy group, difluoromethoxy group and trifluoromethoxy group.

The heterocyclic group which is the substitutent (Rsb) has a nitrogen atom as a hetero atom, and is bonded to the ring of the above-mentioned aromatic hydrocarbon group or of the aromatic heterocyclic group through the nitrogen atom, or is a condensed heterocyclic group that is formed as the heterocyclic group is further condensed with an aromatic hydrocarbon ring or an aromatic heterocyclic ring. It is desired that the number of carbon atoms constituting the heterocyclic ring as the substituent (Rsb) is, usually, 2 to 10 and, particularly, 2 to 6. The heterocyclic ring which is the substituent (Rsb) may further include hetero atoms such as oxygen atoms, sulfur atoms or nitrogen atoms in addition to nitrogen atoms bonded to the ring of the aromatic hydrocarbon group or of the aromatic heterocyclic group. The heterocyclic ring as the substituent (Rsb) may further have a substituent (here, the substituent may be the same as those exemplified for the substituent (Rsb)).

Preferred examples of the heterocyclic group which serves as the above-mentioned substituent (Rsb) include morpholino group, piperidino group, pyrrolydinyl group, piperadino group and indolinyl group.

In the group represented by above-mentioned formula (6), —W[(C₂H₄O)_(x)(C₃H₆O)_(y)(C₄H₈O)_(z)]_(a)—V, it is desired that W is —CH₂O—, —OC(═O)— or an oxygen atom and is, most desirably, an oxygen atom among those described above from the standpoint of photochromic properties and easy synthesis. From the standpoint of favorable compatibility to a high-molecular solid matrix, further, it is desired that V is a (meth)acryloyl group. As the alkyl group R^(a) having 1 to 20 carbon atoms, there can be exemplified a methyl group, an ethyl group, a t-butyl group, a t-octyl group, a decyl group and a stearyl group. Among them, it is particularly desired to use the one having 1 to 6 carbon atoms.

In the formula (6), it is desired that x, y and z are integers of 0 to 20, and that the total number of x, y and z is 1 to 20.

Concerning the group V in the formula (6), there is no particular limitation on a group having an epoxy group with 1 to 5 carbon atoms. Preferably, however, there are exemplified an epoxy group and a glycidyl group and, particularly, a glycidyl group. As a group having a carboxyl group with 1 to 5 carbon atoms, there can be preferably exemplified an alkyl group having a carboxyl group, such as —CH₂CO₂H and —CH(CH₃)CO₂H, as well as —C(═O) (CH₂)CO₂H. As the aminoalkyl group having 1 to 6 carbon atoms, there can be exemplified 2-aminoethyl group and 2-aminobutyl group.

In the group represented by the above-mentioned formula (7), —W[(C₂H₄O)_(x′)(C₃H₆O)_(y′)(C₄H₈O)_(z′)]_(b)-T-[(C₂H₄O)_(x″)(C₃H₆O)_(y″)(C₄H₈O)_(z″)]_(c)—V, the divalent organic residue (containing a cyclic group and having 5 to 20 carbon atoms) denoted by T is typically a hydrocarbon group. Not being limited thereto only, however, the divalent organic residue T may be a group containing such a bond as ester bond, ether bond, amide bond, thioether bond, sulfonyl bond or urethane bond other than carbon-carbon bond. The cyclic group contained in the organic residue may be any one of aliphtatic hydrocarbon ring, heterocyclic ring or aromatic hydrocarbon ring, and the aliphatic hydrocarbon ring and the heterocyclic ring may be those of the crosslinked type. These rings may be 4- to 8-membered rings, or may be those formed by the condensation of 2 to 4 of these rings.

In the present invention, it is desired that the organic residue contains the above-mentioned rings in a plural number and, desirably, in a number of 2 to 4. Concrete examples of the organic residue include those which contain a benzene ring, a cyclohexane ring or an adamantane ring as represented by the following formulas,

In the present invention, an organic residue represented by

is most desired from the standpoint of obtaining more favorable photochromic properties.

In the present invention, further, the above-mentioned substituent (Rsb) is, particularly preferably, a alkyl group; alkoxy group; aralkyl group; amino group; substituted amino group; halogen atom; halogenoalkyl group; or substituted or unsubstituted heterocyclic group having nitrogen atom as a hetero atom, and is bonded via the nitrogen atom.

There is no particular limitation on the positions to where the above substituents (Rsb) are bonded and on the total number thereof.

In the present invention, when the trivalent group represented by the above-mentioned formula (2) or (3) is the one derived from a benzene ring that is described below, it is desired that the alkoxy group is bonded to the fifth position thereof or a nitrogen atom (hetero atom) of the substituted or unsubstituted heterocyclic group is bonded to the fifth position thereof from the standpoint of improving the color density.

Divalent group Z.

In the above general formula (1), the divalent group Z (-Z-) is represented by the following formula (4) or (5),

In the above formulas (4) and (5), the groups represented by R⁷, R⁸ and R⁹ are, independently from each other, alkylene groups, the groups represented by B and B′ are, independently from each other, imino groups, substituted imino groups, oxy groups, thio groups, carbonyl groups, cycloalkylene groups, cycloalkylidene groups, or substituted or unsubstituted arylene groups, and m, n, p and q are 0 or 1.

Though there is no particular limitation, the alkylene groups represented by R⁷ to R⁹ are, desirably, those having 1 to 6 carbon atoms. Preferred examples of the alkylene group include straight-chain or branched-chain groups, such as methylene group, ethylene group, trimethylene group, tetramethylene group, propylene group, tetramethylethylene group and isopropylidene group.

The substituted imino groups represented B and B′ are the ones represented by —NR′—, wherein the group R′ may be the one that complies with the substituent (Rsb). Particularly preferred group R′ may be an alkyl group with 1 to 6 carbon atoms, such as methyl group, ethyl group or propyl group, or a benzyl group.

As the cycloalkylene groups represented by B and B′, there can be exemplified those having 3 to 20 carbon atoms and, preferably, 4 to 12 carbon atoms, such as cyclopropylene group, cyclobutylene group, cyclopentylene group, cyclohexylene group, cycloheptylene group, cyclooctylene group, cyclononylene group and cyclodecylene group.

As the cycloalkylidene groups represented by B and B′, there can be exemplified those having 4 to 20 carbon atoms and, preferably, 4 to 12 carbon atoms, such as cyclobutylidene group, cyclopentylidene group, cyclohexylidene group, cycloheptylidene group, cyclooctylidene group and cyclononylidene group.

As the unsubstituted arylene groups represented by B and B′, there can be exemplified those having 6 to 18 carbon atoms. Concrete examples of the arylene group include phenylene group, naphthylene group and phenanthrylene group.

As the substituted arylene groups represented by B and B′, there can be exemplified those in which 1 or 2 or more hydrogen atoms in the unsubstituted arylene group are substituted by the alkyl group, alkoxy group, aralkyl group, aralkoxy group, amino group, substituted amino group, cycano group or nitro group, which are the same as those descirbed with reference to the above-mentioned substituent (Rsb).

In the present invention, the above-mentioned divalent group Z exhibits the effect of increasing the fading rate and to develop a color tone of a neutral tint. From the degree of effect and easy synthesis, here, it is desired that the groups B and b′ are oxy groups, imino groups, substituted imino groups, cycloalkylene groups, cycloalkylidene groups, or substituted or unsubstituted arylene groups. Groups R¹ to R⁴.

In the above general formula (1), the groups R¹, R², R³ and R⁴ are, independently from each other, hydrogen atoms, hydroxyl groups, alkyl groups, alkoxy groups, aralkyl groups, aralkoxy groups, amino groups, substituted amino groups, cyano groups, nitro groups, halogen atoms, halogenoalkyl groups or halogenoalkoxy groups. Among these groups, those that overlap on the groups described as the above substituents (Rsb) are the same as such groups.

Further, R¹ and R² together or R³ and R⁴ together may form a ring, and either R¹ or R² and either R³ or R⁴ together may form a ring. The thus formed ring may be either an aliphatic hydrocarbon ring or a heterocyclic ring, but is, more preferably, the aliphatic hydrocarbon ring. Further, these rings may have a substituent, and the number of atoms forming the ring is, desirably, from 3 to 20.

As the aliphatic hydrocarbon ring, there can be exemplified monocyclic rings having 3 to 20 carbon atoms, such as cyclopropane ring, cyclobutane ring, cyclopentane ring, cyclohexane ring, cycloheptane ring, cyclooctane ring, cyclononane ring, cyclodecane ring, cycloundecane ring, cyclododecane ring, cyclotridecane ring and cyclopentadodecane ring, or crosslinked aliphatic rings having 6 to 20 carbon atoms, such as bicyclo[2,2,1]heptane ring, bicyclo[2,2,2]octane ring, bicyclo[3,2,0]heptane ring, bicyclo[3,1,1]heptane ring, bicyclo[3,2,1]octane ring and adamantane ring. In the crosslinked aliphatic ring, there is no particular limitation on the positions of the bonding hands. Further, the aliphatic hydrocarbon ring may have a substituent which may be an alkyl group, a cycloalkyl group, an alkoxy group, an amino group or a substituted amino group described above as the substituent (Rsb). There is no particular limitation on the positions and the number of the substituents.

As the heterocyclic group, there can be exemplified oxygen-containing rings such as tetrahydrofurane ring and pyran ring; nitrogen-containing rings such as pyrrolidine ring, piperidine ring, morpholine ring, thiomorpholine ring, piperadine ring and hexamethyleneimine ring; carbonyl-containing rings such as cyclopentanone ring and cyclohexanone ring; ester-containing rings or oxygen-containing carbonyl mixed rings, such as butylolactone ring, tetrahydrofuranon ring and tetrahydropyranon ring; amide-containing rings or nitrogen-containing carbonyl mixed spiro rings, such as pyrrolidinone ring, piperidinone ring and oxohexamethyleneimine rings; and crosslinked rings, such as aza-bicyclo[2,2,2]octane ring, decahydro-cyclopentaazepine ring, aza-bicyclo[3,2,1]octane ring, octahydro-quinolizine ring, decahydro-pyridinoquinoline ring and aza-tricycloundecane ring.

As the substituent of the heterocyclic ring, there can be exemplified alkyl group, cycloalkyl group, alkoxy group, amino group, and substituted amino group that were exemplified above as the substituents (Rsb), and there is no limitation on the positions where the substituents are substituted or on the total number of the substituents.

When either R¹ or R² forms a ring together with either R³ or R⁴, it is desired that the substituent is a crosslinked aliphatic hydrocarbon ring having 7 to 18 carbon atoms among the above-mentioned rings, such as bicyclo[2,2,1]heptane ring, bicyclo[2,2,2]octane ring, bicyclo[3,2,1]octane ring, bicyclo[3,3,1]nonane ring or adamantane ring, or a crosslinked heterocyclic ring having 6 to 18 carbon atoms for forming a ring, such as aza-bicyclo[2,2,2]octane ring, decahydro-cyclopentaazepine ring, or aza-bicyclo[3,2,1]octane ring.

The ring formed by either R¹ or R² and by either R³ or R¹ may be an aromatic hydrocarbon ring such as fluorene ring or phenanthrene ring.

In the present invention, a particularly preferred embodiment is that R¹ to R⁴ are hydrogen atoms, alkyl groups, alkoxy groups or halogenoalkyl groups, R¹ and R² together and/or R³ and R⁴ together are forming rings, or either R¹ or R² and either R³ or R⁴ together are forming a ring. Among them, the effect of quick fading rate is particularly favorably exhibited when a ring is formed by R¹ to R⁴, which is more desirable. In this case, the effect of the present invention is exhibited most distinctly when the ring is formed by the atoms of a number of 5 to 12.

Groups R⁵ and R⁶.

In the above-mentioned general formula (1), R⁵ and R⁶ are, independently from each other, alkyl groups, substituted or unsubstituted aryl groups, or substituted or unsubstituted heteroaryl groups. Here, R⁵ and R⁶ together may form a ring.

Here, the alkyl group, substituted or unsubstituted aryl group, or substituted or unsubstituted heteroaryl group are the same as those groups described as the substituents (Rsb).

Like the ring formed by R¹ to R mentioned above, the ring formed by R⁵ and R⁶ may be any one of aliphatic hydrocarbon ring, heterocyclic ring or aromatic hydrocarbon ring. Preferred examples of the aliphatic hydrocarbon ring include crosslinked rings having 6 to 18 carbon atoms, such as bicyclo[2,2,1]heptane ring, bicyclo[2,2,2]octane ring, bicyclo[3,2,1]octane ring and bicyclo[3.3.1]nonane ring. Preferred examples of the heterocyclic ring include crosslinked rings having 6 to 18 carbon atoms, such as aza-bicyclo[2,2,2]octane ring, decahydro-cyclopentaazepine ring, and aza-bicyclo[3,2,1]octane ring, and preferred examples of the aromatic hydrocarbon ring include those having 10 to 18 carbon atoms, such as fluorene ring and phenanthrene ring.

Further, the ring formed by R⁵ and R⁶, too, may have a substituent which may be alkyl group, alkoxy group, aryl group, hydroxyl group or halogen atom like the ones described concerning the substituent (Rsb).

In the present invention, it is particularly desired that at least either R⁵ or R⁶ is any one of the groups (i) to (iv) described below.

-   (i) An unsubstituted aryl group. -   (ii) A substituted aryl group having, as a substituent, substituted     amino group, alkyl group, cycloalkyl group or alkoxy group. -   (iii) A substituted aryl group in which the substituent is a     heterocyclic group having a nitrogen as a hetero atom and is bonded     to the aryl group via the nitrogen atom (this heterocyclic group may     further have a substituent). -   (iv) The same substituted aryl group as that of -   (iii) above in which a heterocyclic group which is the substituent     is forming a condensed heterocyclic group being condenssed with the     aromatic hydrocarbon ring or the aromatic heterocyclic ring.

In the substituted aryl groups of (ii) to (iv) described above, there is no particular limitation on the positions of the substituents bonded to the aryl group or on the total number of the substitutents. When the aryl group is a phenyl group, however, it is desired that the position of the substituent is the third position or the fourth position, and the number of the substituents is 1 or 2. Concrete examples of the preferred substituted phenyl group include 4-(N,N-dimethyllamino)phenyl group, 4-(N,N,-diethylamino)phenyl group, 4-(N,N-diphenylamino)phenyl group, 4-morpholinophenyl group, 4-piperidinophenyl group, 4-methoxyphenyl group, 4-ethoxyphenyl group, 4-propoxyphenyl group, 4-butoxyphenyl group, 4-cyclohexylphenyl group, and 3,4-dimethoxyphenyl group. When the aryl group is the one other than the phenylgroup, it is desired that the number of the substituent is 1. Preferred examples of the substituted aryl group include 4-(N,N-dimethylamino)thienyl group, 4-(N,N-diethylamino)furyl group, 4-(N,N-diphenylamino)thienyl group, 4-morpholinopyrrolinyl group, 6-piperidinobenzothienyl group, and 6-(N,N-dimethylamino)benzofuranyl group. Chromene compounds.

The compound of the present invention expressed by the above-mentioned general formula (1) usually exists as a colorless sold at normal temperature and under normal pressure, and can be confirmed by the following means {circle around (1)} to {circle around (3)}.

-   {circle around (1)} Measurement of a proton nuclear magnetic     resonance spectrum (¹H-NMR) indicates peaks based on an aromatic     proton and an alkene proton near δ5.9 to 9.0 ppm and peaks based on     an alkyl group and an alkylene group near δ1.0 to 4.0 ppm. Upon     relatively comparing the spectrum intensities at these peaks,     further, the numbers of protons in the bonding groups can be known. -   {circle around (2)} The compositions of the corresponding products     can be determined by the elemental analysis. -   {circle around (3)} Measurement of a ¹³C-nuclear magnetic resonance     spectrum (¹³C-NMR) indicates a peak based on a carbon atom of an     aromatic hydrocarbon group near δ110 to 160 ppm, a peak based on a     carbon atom of alkene near δ80 to 140 ppm, and peaks based on carbon     atoms of an alkyl group and an alkylene group near δ20 to 80 ppm.

The chromene compound of the present invention represented by the above-mentioned general formula (1) exhibits excellent photochromic properties such as small initial color, large fading rate, excellent light resistance while developing a color tone of a neutral tint. Among the chromene compounds of the present invention, the most excellent photochromic characteristics are exhibited by the following compounds.

Though there is no particular limitation, the chromene compound of the present invention can be produced by, for example, a method described below (in the general formulas (8) and (9) representing a naphthol derivative and a propargyl alcohol used in the following production process, the groups R¹ to R⁶, rings X and Y, and the divalent group Z are as defined in the general formula (1)).

Namely, a chromene compound represented by the above general formula (1) is obtained by reacting a naphthol derivative represented by the following general formula (8),

with a propargyl alcohol derivative represented by the following general formula (9),

in the presence of an acid catalyst.

In the reaction in the presence of the acid catalyst, though there is no particular limitation, the naphthol derivative and the propargyl alcohol derivative are usually used at a ratio satisfying molar ratios of 1:10 to 10:1.

As the acid catalyst, further, there is used sulfuric acid, benzenesulfonic acid, p-toluenebenzenesulfonic acid or acidic alumina in an amount of from 0.1 to 10 parts by weight per the toal amount of 100 parts by weight of the naphthol derivative and the propargyl alcohol derivative.

The reaction temperature is usually 0 to 200° C., and the solvent is a non-protonic organic solvent, such as N-methylpyrrolidone, dimethylformamide, tetrahydrofurane, benzene or toluene.

The chromene compound of the present invention obtained through the above reaction dissolves well in a general organic solvent such as toluene, chloroform or tetrahydrofurane. A solution obtained by dissolving the chromene compound in the above solvent is, usually, colorless and transparent, and exhibits a favorable reversible photochromic action quickly developing a color when it is irradiated with sunlight or ultraviolet rays and quickly returning to the initial colorless state when it is shut off the light.

The above photochromic action of the chromene compound of the present invention is similarly exhibited even in a high-molecular solid matrix. The high-molecular solid matrix may be the one in which the chromene compound of the present invention disperses homogeneously. Optically preferred examples include such thermoplastic resins as polymethylacrylate, polyethylacrylate, polymethylmethacrylate, polyethylmethacrylate, polystyrene, polyacrylonitrile, polyvinyl alcohol, polyacrylamide, poly(2-hydroxyethyl methacrylate), polydimethylsiloxane, polyethylene glycol monoallyl ether, and polycarbonate.

A curable resin obtained by polymerizing a radically polymerizable polyfunctional monomer, too, can be used as a high-molecular solid matrix. In the above curable resin, examples of the radically polymerizable polyfunctional monomer include polyvalent acrylic acid and polyvalent methacrylic acid ester compounds, such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycolate dimethacrylate, ethylene glycol bisglycidyl methacrylate, polyethylene glycol diacrylate, urethane oligomer hexaacrylate, bisphenol A dimethacrylate, trimethylolpropane trimethacrylate, 2,2-bis(4-methacryloyloxyethoxyphenyl)propane, and 2,2-bis(3,5-dibromo-4-methacryloyloxyethoxyphenyl)propane; polyvalent allyl compounds, such as diallyl phthalate, diallyl terephthalate, diallyl isophthalate, diallyl tartarate, diallyl epoxysuccinate, diallyl fumarate, diallyl chloroendoate, diallyl hexaphthalate, diallyl carbonate, allyl diglycol carbonate and trimethylolpropanetriallyl carbonate; polyvalent thioacrylic acid and polyvalent thiomethacrylic acid ester compounds, such as 1,2-bis(methacryloylthio)ethane, bis(2-acryloylthioethyl)ether, and 1,4-bis(methacryloylthiomethyl)benzene; acrylic acid ester compounds and methacrylic acid ester compounds, such as glycidyl acrylate, glycidyl methacrylate, γ-methacryloyloxypropyltrimethoxy silane, β-methylglycidyl methacrylate, bisphenol A monoglycidyl ether methacrylate, 4-glycidyloxy methacrylate, 3-(glycidyl-2-oxyethoxy)-2-hydroxypropyl methacrylate, 3-(glycidyloxy-1-isopropyloxy)-2-hydroxypropyl acrylate, and 3-glycidyloxy-2-hydroxypropyloxy)-2-hydroxypropyl acrylate; and divinyl benzene.

A copolymer of the above radically polymerizable polyfunctional monomer and a monofunctional radical polymer, too, can be used as a high-molecular solid matrix. As the monofunctional radical polymer, there can be exemplified unsaturated carboxylic acid, such as acrylic acid, methacrylic acid and maleic anhydride; acrylic acid and methacrylic acid ester compounds, such as methyl acrylate, methyl methacrylate, benzyl methacrylate, phenyl methacrylate and 2-hydroxyethyl methacrylate; fumaric acid ester compounds such as diethyl fumarate and diphenyl fumarate; thioacrylic acid and thiomethacrylic acid ester compounds, such as methyl thioacrylate, benzyl thioacrylate and benzyl thiomethacrylate; and vinyl compounds, such as styrene, chlorostyrene, methylstyrene, vinylnaphthalene, α-methylstyrene dimer and bromostyrene.

When the above-mentioned radically polymerizable monomer is to be polymerized by the irradiation with ultraviolet rays, there is preferably used, as a photopolymerization initiator, benzoin, benzoinmethyl ether, benzoinbutyl ether, benzophenol, acetophenone 4,4′-dichlorobenzophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-on, benzylmethylketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-on, 1-hydroxycyclohexylphenyl ketone, 2-isopropylthioxanthone, bis(2,6-dimethoxybenzoyl-2,4,4-trimethyl-pentyl phosphineoxide, bis(2,4-6-trimethylbenzoyl)-phenyl phosphineoxide, 2,4,6-trimethylbenzoyldiphenyl phosphineoxide, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1.

There is no particular limitation on the method of dispersing the chromene compound of the present invention in the above-mentioned high-molecular solid matrix, and there can be used a generally employed method. For example, there can be exemplified a method of kneading the thermoplastic resin and the chromene compound together in a molten state to disperse the chromene compound in the resin, a method of dissolving a chromene compound in the polymerizable monomer, adding a polymerization catalyst thereto, and effecting the polymerization with heat or light to disperse the chromene compound in the resin, or a method of dyeing the surfaces of the thermoplastic resin and of the curable resin with a chromene compound, so that the chromene compound disperses in the resin.

The chromene compound of the present invention can be used as a photochromic material over a wide range, such as various memory materials to substitute for silver salt photosensitive materials, i.e., can be used as a copying material, a photosensitive material for printing, a memory material for cathode-ray tubes, a photosensitive material for lasers and as a photosensitive material for holography. Further, the photochromic material using the chromene compound of the present invention can be utilized as a photochromic lens material, an optical filter material, a display material, an actinometer and as an ornamental material.

For photochromic lenses, for example, the chromene compound of the present invention can be used by any method so far as there is obtained a homogeneous dimming property. Concretely speaking, the chromene compound of the present invention is used by a variety of methods such as a method by which a polymer film in which the chromene compound of the present invention is homogeneously dispersed, is sandwiched in the lens or is laminated thereon; a method by which the chromene compound of the invention is dispersed in the polymerizable monomer and is polymerized according to a predetermined method to obtain a photochromic lens; a method by which the chromene compound of the present invention is dispersed in the polymerizable monomer to prepare a photochromic monomer composition, and the monomer composition is applied to the surfaces of a non-photochromic lens material to obtain a lens on which a photochromic film is laminated; a method by which the chromene compound of the present invention is dissolved in, for example, a silicone oil, and the lens surfaces are impregnated with the chromene compound at 150 to 200° C. over a period of 10 to 60 minutes and, then, the surfaces thereof are coated with a curable material to obtain a photochromic lens; or a method by which a polymer film in which the chromene compound of the invention has been homogeneously dispersed is formed on the surface of the lens which is, then, coated with a curable material to obtain a photochromic lens.

The chromene compound of the present invention exhibits a high fading rate in a solution or in a high-molecular solid matrix. Besides, in a state of not being irradiated with light, the chromene compound of the invention exhibits little color. Even after used for extended periods of time, the chromene compound of the invention exhibits little color yet maintaining good photochromic property. For example, the photochromic lens using the chromene compound of the present invention quickly resumes its initial color tone when it is brought indoors from outdoors and, further exhibits little color even after used for extended periods of time, thus featuring good light resistance.

When placed in a state of developing color, further, the chromene compound of the present invention exhibits two absorption bands of from 420 to 520 nm and from 520 to 620 nm, producing a small difference in the intensity of absorption between the two bands and a ratio of color densities of usually in a range of from 0.7 to 1.5. It is, therefore, possible to develop a color tone of a neutral tint such as grey or brown even by using a single compound.

EXAMPLES

The present invention will be described in further detail by way of Examples to which only, however, the invention is in no way limited.

Example 1

6.3 Grams (0.02 mols) of a naphthol derivative of the following formula,

and 5.5 g (0.022 mols) of a propargyl alcohol derivative of the following formula,

were dissolved in 50 ml of toluene, followed by the addition of 0.05 g of a p-toluenesulfonic acid, and the mixture was stirred at a refluxing temperature for one hour. After the reaction, the solvent was distilled off, and the reaction product was refined by a chromatography on silica gel to obtain 3.1 g of a pale bluish powdery product, yield, 28%.

The values of elemental analysis of the product were:

-   -   C: 85.44%     -   H: 6.02%     -   N: 2.57%     -   O: 5.97%         which were in very good agreement with the calculated values (C:         85.53%, H: 6.07%, N: 2.56%, O: 5.84%) of C₂₉H₃₃NO₂.

Measurement of the proton nuclear magnetic resonance spectrum indicated a peak of 16 H based on an alkylene group near δ1.0 to 4.0 ppm, and peaks of 17H based on an aromatic proton and on an alkene proton near δ5.6 to 9.0 ppm.

Further, measurement of a 13C-nuclear magnetic resonance spectrum indicated a peak based on a carbon atom of an aromatic ring near δ110 to 160 ppm, a peak based on a carbon atom of an alkene near δ80 to 140 ppm, and a peak based on a carbon atom of an alkyl at δ20 to 60 ppm.

From the above results, it was confirmed that the isolated product was a compound represented by the following structural formula. FIG. 1 shows a ¹H-NMR spectrum of the compound that was obtained.

Examples 2 to 22

Chromene compounds shown in Tables 1 to 6 were synthesized in the same manner as in Example 1. The obtained products were analyzed for their structures by using the same structure confirmation means as that of Example 1 to make sure that the compounds possessed the structures represented by the structural formulas shown in Tables 1 to 6. Tables 7 and 8 show values of elemental analyses of these compounds as well as values found from the structural formulas of these compounds.

TABLE 1 Starting material Ex. No. Naphthol derivative Propargyl alcohol 2

3

4

5

Ex. No. Product Yield (%) 2

21 3

16 4

33 5

27

TABLE 2 Starting material Ex. No. Naphthol derivative Propargyl alcohol 6

7

8

9

Ex. No. Product Yield (%) 6

26 7

22 8

29 9

27

TABLE 3 Starting material Ex. No. Naphthol derivative Propargyl alcohol 10

11

12

13

Yield Ex. No. Product (%) 10

16 11

19 12

21 13

17

TABLE 4 Starting material Ex. No. Naphthol derivative Propargyl alcohol 14

15

16

17

Ex. No. Product Yield (%) 14

22 15

24 16

31 17

19

TABLE 5 Starting material Ex. No. Naphthol derivative Propargyl alcohol 18

19

20

Ex. No. Product Yield (%) 18

22 19

21 20

26

TABLE 6 Starting material Ex. No. Naphtol derivative Propargyl alcohol 21

22

Yield Ex. No. Product (%) 21

21 22

14

TABLE 7 Element analysis Ex. Found Calculated ¹H-NMR No. C H N O Others C H N O Others (NMR) 2 67.62 4.48 1.91 10.72 F: 67.65 4.46 1.88 10.73 F: δ5.6˜9.0 16H 15.27 15.29 δ1.0˜4.0 17H 3 81.7 6.58 4.31 7.41 81.7 6.54 4.33 7.42 δ5.6˜9.0 15H δ1.0˜4.0 27H 4 88.13 6.91 2.31 2.65 88.11 6.89 2.34 2.67 δ5.6˜9.0 17H δ1.0˜4.0 24H 5 80.77 6.45 2.29 10.49 80.76 6.45 2.3 10.5 δ5.6˜9.0 14H δ1.0˜4.0 25H 6 88.95 6.12 2.28 2.65 88.93 6.14 2.3 2.63 δ5.6˜9.0 21H δ1.0˜4.0 16H 7 83.28 6.46 2.32 7.94 83.27 6.49 2.31 7.92 δ5.6˜9.0 16H δ1.0˜4.0 23H 8 81.67 6.55 2.12 9.67 81.69 6.54 2.12 9.65 δ5.6˜9.0 15H δ1.0˜4.0 28H 9 85.38 6.09 8.53 85.39 6.08 8.53 δ5.6˜9.0 16H δ1.0˜4.0 18H 10 85.52 5.86 2.62 6 85.51 5.88 2.6 6.01 δ5.6˜9.0 16H δ1.0˜4.0 15H 11 87.36 6.49 3.92 2.24 87.38 6.48 3.9 2.24 δ5.6˜9.0 22H δ1.0˜4.0 24H

TABLE 8 Element analysis Ex. Found Calculated ¹H-NMR No. C H N O Others C H N O Others (NMR) 12 85.39 7.33 4.63 2.65 85.38 7.33 4.61 2.68 δ5.6˜9.0 17H δ1.0˜4.0 27H 13 80.12 5.45 8.65 S: 80.12 5.44 8.64 S: δ5.6˜9.0 15H 5.78 5.80 δ1.0˜4.0 15H 14 78.67 5.36 3.82 4.37 F: 78.66 5.33 3.81 4.39 F: δ5.6˜9.0 21H 7.78 7.81 δ1.0˜4.0 18H 15 84.86 6.71 1.9 6.52 84.89 6.69 1.91 6.51 δ5.6˜9.0 18H δ1.0˜4.0 31H 16 85.37 5.88 8.75 85.35 5.89 8.76 δ5.6˜9.0 16H δ1.0˜4.0 16H 17 84.47 7.6 1.79 6.14 84.49 7.59 1.78 6.14 δ5.6˜9.0 15H δ1.0˜4.0 44H 18 81.3 6.67 12.03 81.33 6.61 12.06 δ5.6˜9.0 14H δ1.0˜4.0 30H 19 88.85 6.71 2.07 2.37 88.88 6.72 2.04 2.36 δ5.6˜9.0 19H δ1.0˜4.0 26H 20 81 6.15 12.85 81.03 6.14 12.83 δ5.6˜9.0 16H δ1.0˜4.0 33H 21 79.03 6.5 1.84 12.63 79.05 6.51 1.84 12.6 δ5.6˜9.0 14H δ1.0˜4.0 24H 22 79.27 6.95 1.36 12.42 79.16 6.99 1.34 12.51 δ5.6˜9.0 24H δ1.0˜4.0 47H

Applied Examples

Each of the chromene compounds obtained in Examples 1 to 22 in an amount of 0.04 parts by weight, were added to 13 parts by weight of a tetraethylene glycol dimethacrylate, 48 parts by weight of a 2,2-bis[4-(methacryloxyethoxy)phenyl]propane, 2 parts by weight of a polyethylene glycol monoallyl ether, 20 parts by weight of a trimethylolpropane trimethacrylate, and 9 parts by weight of a glycidyl methacrylate, and to which was further added, as a polymerization initiator, 1 part by weight of a t-butylperoxy 2-ethyl hexanate, and the mixture was mixed together to a sufficient degree.

The mixture was poured into a mold constituted by glass plates and a gasket of an ethylene/vinyl acetate copolymer, and was cast-polymerized. The polymerization was conducted by using an air furnace while gradually raising the temperature from 30° C. to 90° C. over 18 hours, and the temperature of 90° C. was maintained for 2 hours. After the polymerization, the polymer was taken out from the glass mold.

The obtained polymer (sample having a thickness of 2 mm) was irradiated with light by using a xenon lamp L-2480 (300W) SHL-100 manufactured by Hamamatsu Photonics Co. through an aeromass filter (manufactured by Coning Co.) at a temperature of 20±1° C. at beam intensities on the polymer surface of 2.4 mW/cm² (365 nm) and 24 μW/cm² (245 nm) for 120 seconds to develop color and to measure the photochromic properties of the sample. The photochromic properties were evaluated by the following methods, and were as shown in Tables 9 and 10.

-   {circle around (1)} Maximum absorption wavelength (λmax): A maximum     absorption wavelength after the development of color was found by     using a spectrophotometer (instantaneous multi-channel photodetector     MCPD 1000) manufactured by Otsuka Denshi Co. The maximum absorption     wavelength is related to the color tone at the time when the color     is developed. -   {circle around (2)} Color density {ε(120)−ε(0)}: A difference     between an absorbancy ε(120) after irradiated with light for 120     seconds at a maximum absorption wavelength and ε(0) in a state of     not irradiated with light. It can be said that the higher this     value, the more excellent the photochromic properties are. -   {circle around (3)} Fading rate {τ1/2 (min.)}: The time until the     absorbency of a sample at a maximum wavelength drops down to     one-half the {ε(120)−ε(0)} from when the sample is no longer     irradiated with light after it was irradiated with light for 120     seconds. It can be said that the shorter the time, the more     excellent the photochromic properties are. -   {circle around (4)} Initial color (YI): The coloring degree was     measured by using a color difference meter (SM-4) manufactured by     Suga Shikenki Co. It can be said that the smaller the value YI, the     smaller the coloring degree in a state of not being irradiated with     light, which is excellent. -   {circle around (5)} Remaining factor (%): The following     deterioration promotion testing was conducted in order to evaluate     the light resistance of color developed by the irradiation with     light. That is, the obtained polymer (sample) was deteriorated by     using a xenon weather meter X25 manufactured by Suga Shikenki Co.     for 200 hours. Thereafter, the color densities were evaluated before     and after the testing; i.e., a color density (A0) before the testing     and a color density (A200) after the testing were measured, and a     value {(A200/A0)×100} was calculated as a remaining factor (%) to     use it as an index of resistance of the developed color. The higher     the remaining factor, the higher the resistance of the developed     color. -   {circle around (6)} Ratio of color densities: A ratio of absorbancy     at a maximum absorption wavelength was calculated in compliance with     the formula [{ε1(120)−ε1(0)}/{ε2 (120)−ε2(0)}]     -   where ε1 is an absorbancy at a maximum absorption wavelength on         the side of the short wavelength,     -   and ε2 is an absorbancy at a maximum absorption wavelength on         the side of the long wavelength,         and is used as an index of developing a color tone of a neutral         tint. A favorable neutral tint is obtained as the density ratio         approaches 1.

TABLE 9 Ex. λmax Color density Fading rate Initial color Remaining factor Color No. (nm) ε (120)-ε (0) τ½(min.) YI {A200/A0} × 100} density ratio 1 482 0.88 0.6 9 76 0.90 582 0.98 0.6 2 490 0.96 1.3 8 81 0.97 592 0.99 1.3 3 464 1.18 0.8 10 83 1.20 590 0.98 0.8 4 484 0.79 0.5 4 86 0.93 588 0.85 0.5 5 498 0.84 1.4 6 82 1.14 596 0.74 1.4 6 486 0.83 0.6 7 82 0.97 588 0.86 0.6 7 488 0.92 0.6 7 82 0.95 598 0.97 0.6 8 482 0.92 1.0 6 80 0.85 584 1.08 1.0 9 424 1.18 1.4 6 81 0.98 538 1.21 1.4 10 444 0.72 1.2 10 77 0.82 562 0.88 1.2 11 492 0.92 0.6 11 72 1.10 598 0.84 0.6

TABLE 10 Ex. λmax Color density Fading rate Initial color Remaining factor Color No. (nm) ε (120)-ε (0) τ½(min.) YI {A200/A0} × 100} density ratio 12 494 0.72 0.5 4 81 0.90 600 0.80 0.5 13 482 0.79 1.3 10 75 0.85 584 0.93 1.3 14 462 0.71 0.7 8 83 0.88 588 0.81 0.7 15 482 0.55 0.4 8 79 0.76 596 0.72 0.4 16 448 1.09 0.7 9 81 1.18 540 0.92 0.7 17 426 1.21 0.7 11 78 1.38 546 0.88 0.7 18 482 1.02 1.4 6 82 0.89 562 1.15 1.4 19 492 1.18 1.5 15 73 0.94 608 1.25 1.5 20 434 1.22 1.7 8 79 1.09 532 1.12 1.7 21 478 0.78 1.3 6 82 0.85 584 0.92 1.3 22 482 0.88 1.4 7 83 0.86 592 1.02 1.4

Comparative Examples 1 to 3

For comparison, photochromic polymers were obtained in the same manner as the above applied Examples but using the compounds represented by the following formulas (A), (B) and (C),

and their properties were evaluated. The results were as shown in Table 11.

TABLE 11 Color Fading Coloring Remaining Color Comp. Compound λmax density rate degree factor density Ex. No. No. (nm) ε (120)-ε (0) τ½(min.) YI {A200/A0} × 100} ratio 1 A 522 0.86 8.3 3 68 — 2 B 498 0.92 4.1 4 71 1.10 596 0.84 4.1 3 C 484 0.45 1.3 14  77 0.50 610 0.90 1.3

Examples 1 to 22 using the chromene compounds of the present invention are superior in three effects, i.e., fading rate, initial color and color density ratio, to those of Comparative Examples 1 to 3. 

1. A chromene compound represented by the following formula (1),

wherein R¹, R², R³ and R⁴ are, independently from each other, hydrogen atoms, hydroxyl groups, alkyl groups, alkoxy groups, aralkyl groups, aralkoxy groups, amino groups, substituted amino groups, cyano groups, nitro groups, halogen atoms, halogenoalkyl groups or halogenoalkoxy groups, R¹ and R² together, and R³ and R⁴ together, may form rings, and either R¹ or R² and either R³ or R⁴ together may form a ring, R⁵ and R⁶ are, independently from each other, alkyl groups, substituted or unsubstituted aryl groups, or substituted or unsubstituted heteroaryl groups, or R⁵ and R⁶ together may form a ring, a trivalent cyclic group represented by the following formula (2),

and a trivalent cyclic group represented by the following formula (3),

are, independently from each other, substituted or unsubsttituted aromatic hydrocarbon groups or substituted or unsubstituted aromatic heterocyclic groups, and a divalent group Z is presented by the following formula (4) or (5),

wherein R⁷, R⁸ and R⁹ are, independently from each other, alkylene groups, B and B′ are, independently from each other, imino groups, substituted imino groups, oxy groups, thio groups, carbonyl groups, cycloalkylene groups, cycloalkylidene groups, or substituted or unsubstituted arylene groups, and m, n, p and q are 0 or
 1. 2. A chromene compound according to claim 1, wherein in the formulas (4) and (5), the groups represented by R⁷, R⁸ and R⁹ are, independently from each other, alkylene groups having 1 to 6 carbon atoms, the groups represented by B and B′ are, independently from each other, imino groups, substituted imino groups, oxy groups, cycloalkylene groups, cycloalkylidene groups, or substituted or unsubstituted arylene groups.
 3. A chromene compound according to claim 1, wherein the trivalent cyclic group represented by the formula (2) or (3) is: (a) a substituted or unsubstituted aromatic hydrocarbon group comprising one benzene ring or a condensed ring formed by the condensation of 2 to 4 benzene rings; (b) an aromatic heterocyclic group comprising an aromatic heterocyclic ring selected from a 5-membered ring or a 6-membered ring containing oxygen atom, sulfur atom or nitrogen atom; (c) a condensed heterocyclic ring in which the above aromatic heterocyclic ring which is the 5-membered ring or the 6-membered ring is condensed with a benzene ring or, further, with a heterocyclic ring; or (d) a condensed heterocyclic group in which the benzene ring is condensed with the above aromatic heterocyclic ring which is the 5-membered ring or the 6-membered ring.
 4. A chromene compound according to claim 1, wherein the trivalent cyclic group represented by the formula (2) or (3) is an aromatic hydrocarbon group or an aromatic heterocyclic group having a substituent which is: a hydroxyl group, an alkyl group, a cycloalkyl group; an alkoxy group, an aralkyl group, an aralkoxy group, an amino group, a substituted amino group, a cyano group, a nitro group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a halogen atom, a halogenoalkyl group, a halogenoalkoxy group, a substituted or unsubstituted heterocyclic group having a nitrogen atom as a hetero atom and is bonded via the nitrogen atom, a condensed heterocyclic group in which the above heterocyclic group is condensed with an aromatic hydrocarbon ring or an aromatic heterocyclic ring; or is a group represented by the following formula (6) —W[(C₂H₄O)_(x)(C₃H₆O)_(y)(C₄H₈O)_(z)]_(a)—V wherein W is —C(═O)O—, —CH₂O—, —OC(═O)—, —N(R^(a))C(═O)—, —N[C(═O)—]₂, —N(R^(a))—, —N(R^(a))CON(H)—, >N—, an oxygen atom or a sulfur atom, x, y and z are integers of 0 to 50, the total number of x, y and z is 1 to 50, a is 1 when W is —C(═O)O—, —CH₂O—, —OC(═O)—, —N(R^(a))C(═O)—, —N(R^(a))—, —N(R^(a))CON(H)—, an oxygen atom or a sulfur atom, and is 2 when W is —N[C(═O)—]₂ or >N—, V is a hydrogen atom, a (meth)acryloyl group, a group having an epoxy group with 1 to 5 carbon atoms, a group having a carboxyl group with 1 to 5 carbon atoms, an oxorane group, an aminoalkyl group with 1 to 6 carbon atoms or an oxylanylmethyl group, and Ra is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms; or is a group represented by the following formula (7) —W[(C₂H₄O)_(x′(C) ₃H₆O)_(y′)(C₄H₈O)_(z′]b-T-[(C) ₂H₄O)_(x″)(C₃H₆O)_(y″)(C₄HO)_(z″)]_(c)—V wherein, T is a divalent organic residue having 5 to 20 carbon atoms and containing a cyclic group, W and V are as defined in the formula (6), and x′, y′, z′, x″, y″ and z″ are the same as x, y and z in the formula (6).
 5. A chromene compound according to claim 1, wherein R¹, R², R³ and R⁴ are, independently from each other, hydrogen atoms, alkyl groups, alkoxy groups, or halogenoalkyl groups.
 6. A chromene compound according to claim 1, wherein R¹ and R² together and/or R³ and R⁴ together form rings.
 7. A chromene compound according to claim 1, wherein either R¹ or R² and either R³ or R⁴ together form a ring.
 8. A chromene compound according to claim 1, wherein R⁵ and R⁶ are substituted aryl groups or substituted heteroaryl groups, and said substitutent is a hydroxyl group, an alkyl group, a cycloalkyl group, an alkoxy group, an aralkyl group, an aralkoxy group, an amino group, a substituted amino group, a cyano group, a nitro group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a halogen atom, a halogenoalkyl group, a halogenoalkoxy group, a substituted or unsubstituted heterocyclic group having a nitrogen atom as a hetero atom and is bonded via the nitrogen atom, a condensed heterocyclic group in which the above heterocyclic group is condensed with an aromatic hydrocarbon ring or an aromatic heterocyclic ring.
 9. A chromene compound according to claim 1, wherein at least either R⁵ or R⁶ is: (i) an unsubstituted aryl group; (ii) a substituted aryl group having, as a substituent, substituted amino group, alkyl group, cycloalkyl group or alkoxy group; (iii) a substituted aryl group in which the substituent is a heterocyclic group having a nitrogen as a hetero atom and is bonded to the aryl group via the nitrogen atom; or (iv) the substituted aryl group of (iii) above in which a heterocyclic group which is the substituent is forming a condensed heterocyclic group being condensed with the aromatic hydrocarbon ring or the aromatic heterocyclic ring.
 10. A photochromic material comprising a chromene compound of claim
 1. 11. A photochromic optical material containing a chromene compound of claim
 1. 